• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.8
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• pp.140-152
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• 1995

Derived was the scalar wave equation of optical fibers. Based on the derived equation, the dispersion characteristics of arbitrarily profiled fibers were analyzed. We applied the 1-D FEM employing quadratic interpolation fucntions to solve the scalar wave equation. To find the optimum index distribution of a fiber that has the ultra-low total dispersion, we analyzed QC fibers as objects. Adding 2$_{nd}$ and 3$_{rd}$ clads to DC fiber, we investigated the change of dispersion characteristics. We found the QC fiber parameters for which the dispersion was ultra-low flattened, less than 0.5 ps/km.nm for ${\lambda}=1.4~1.6{\mu}m$, and the dispersion value was as low as 0.20 ps/km.nm at ${\lambda}=1.55{\mu}m$.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.154-157
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• 2000

Superconducting tape easily can applied to distribution of electricity. It designs basic model of Saturable Reactor type Fault Current Limiter which used superconducting tape, and observes a specific character by means of simulation. Saturable Reactor type Fault Current Limiter is not influenced by saturation of Magnet core appeared in Induction Fault Current Limiter, because it exploit saturation of Iron core. But, it is possible that superconducting tape quenched when AC current flow to superconducting tape which biased DC voltage.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.6-9
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• 1997

The study is analyzed the thrust fon:e of moving type Linear DC Motor(MM-LDM). The MM-LDM consists of a stator (platen) and mover (forcer). One of the method for calculating tile thrust of an MM-LDM is to analyze the energy gradient which is determined by the distribution of magnet flux. However, this method is very difficult when used to calculate the thrust force of this kind of LDM. The stored energy in the MM-LDM can be obtained by measuring the self-inductance and mutual-inductance of equivalent circuit of the MM-LOM and this energy gradient gives the thrust. The calculation of thrust force included in this motor shows that the mutual inductance has large influence on the generation of thrust force.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.274-275
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• 2015

에너지저장장치, 태양광 발전기, 전기자동차 등 직류 사용설비의 급증으로 인해 직류 배전 혹은 직류 마이크로그리드에 대한 관심이 증가하고 있다. 직류 배전은 전력변환을 최소화하여 효율이 높고 수변전 설비 공간이 절약되는 장점이 있다. 하지만 직류를 통해 계통에 연계된 부하와 설비들은 별도의 제어가 없으면 관성과 주파수-부하 반응을 제공할 수 없다. 따라서 직류 배전 투입이 늘어날수록 전력계통의 관성과 주파수-부하 반응이 감소하게 되어 계통 주파수 변동 발생 시 변동 속도와 크기가 증가하게 된다. 때문에 계통 운영자는 더 많은 주파수 조정 예비력을 확보하여야 한다. 본 논문에서는 동요방정식을 이용하여 직류 배전 투입에 따라 계통 관성과 주파수-부하반응이 줄어듦에 따라 변하는 필요 주파수 조정 예비력 량을 계산하는 방법을 제시하고 있으며 MATLAB을 이용하여 직류배전 투입 비율에 따른 필요 주파수 조정 예비력 량 변화를 모의하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.829-836
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• 2003

Understanding of heat generation in semiconductor devices is important in the thermal management of integrated circuits and in the analysis of the device physics. Scanning thermal microscope was used to measure the temperature and the electric potential distribution on the cross-section of an operating metal-oxide-semiconductor field-effect transistor (MOSFET). The temperature distributions were measured both in DC and AC modes in order to take account of the leakage current. The measurement results showed that as the drain bias was increased the hot spot moved to the drain. The density of the iso-potential lines near the drain increased with the increase in the drain bias.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.465-468
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• 2001

An objection of this study is to develop a high stable analytic system of radioactive pulses. The proposed system consists of an amplifying circuit with 60dB gain, a programmable power supply unit which can generate DC voltage up to 1, 500V, and a digital signal processor. Pulse height distribution in accordance with pulse counts is important data in analyzing radioactive pulses. In this study, AD convertor (12bit, l00ns) and DSP (TMS 320C31-60) are used to analyze the pulse height, and the analytic system is designed to be operated in PC-networking.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.111-112
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• 2010

21C 정보화 사회를 맞이하여 디지털 부하의 사용이 급격히 증가하고 있다. 뿐만 아니라 친환경 녹색성장의 일환으로 풍력, 연료전지, 태양광과 같은 신재생 에너지원을 이용한 발전 시스템도 증가 하고 있다. 이에 따라 교류에 비하여 신뢰도가 높고, 저손실의 전원 시스템을 구축할 수 있는 직류급전시스템의 필요성이 부각되고 있다. 직류급전시스템에 있어 효율성, 신뢰성, 전송능력 등이 고려되어야 하지만 직류 배전의 상용화를 위해서는 직류 전용 보호차단기 등을 개발하여 보급하여야 한다. 미국의 통계에 따르면 아크사고는 전기화재의 큰 요인으로 꼽히고 있다. 이미 교류 아크의 검출 알고리즘이 다방면으로 연구되어 아크차단기(AFCI)가 개발되었으며 미국의 경우 AFCI 사용을 법제화 하고 있다. 따라서 직류급전시스템에서의 아크 검출을 위해 직류 아크의 특성을 분석한다.

• Journal of ILASS-Korea
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• v.11 no.3
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• pp.131-139
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• 2006

An experimental study was performed to investigate the liquid breakup and atomization characteristics in electrohydrodynamic atomization according to the changing of experimental parameters such as nozzle size, fluid flow, and electrical intensity. An original electrohydrodynamic atomizer equipment was designed and manufactured for the analysis of spray visualization and the exploration of relationship between applied power and the behavior of liquid atomization. The image processing technique by using the back-illumination method was applied to visualize the distilled liquid breakup process and to examine the variation of the droplet size distribution. The results show that the spray modes of electrohydrodynamic atomization are closelyconnected by the strength of the electric stresses at the surface of the liquid film and the kinetic energy of the liquid jet leaving the needle tip.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.2
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• pp.56-62
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• 1999

This paper is concerned with the design and the construction of a moving magnet type linear DC motor(MM type LDM) for instrumentation. A mathematical model for the design of a LDM is developed and a permeance method is used to calculate the effective flux density in the air gap. The flux distribution in the air gap is analyzed and the width of iron core should be determined in order not to saturate the iron core by caluclating maxmum flux density. The design data culculated by a permeance method are compared with the analyzed results using FEM(MAXWELL 2D). The errors between two results are corrected. The tested LDM is constructed using the corrected design data. The results of experiment for thrust characteristics are compared with simulation.

• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.921-924
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• 2003

A current-voltage relation for Positive Temperature Coefficient of Resistance (PTCR) ceramic was derived and compared with the experimental data. The new current-voltage relation was developed based on Heywangs double Schottky barrier model and a bias distribution across the grain boundary. The voltage limitation V < 4${\Phi}$$\sub$b/ suggested by Heywang is no longer necessary in the new expression for the voltage dependence of the resistance. The pulsed voltages were applied to the PTCR ceramic specimen in order to avoid possible temperature variation during the measurement.